Are Green Walls Better Options than Green Roofs for Mitigating PM 10 Pollution? CFD Simulations in Urban Street Canyons

Hongqiao Qin, Bo Hong and Runsheng Jiang
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Hongqiao Qin: College of Landscape Architecture & Arts, Northwest A&F University, 712100 Yangling, China
Bo Hong: College of Landscape Architecture & Arts, Northwest A&F University, 712100 Yangling, China
Runsheng Jiang: College of Landscape Architecture & Arts, Northwest A&F University, 712100 Yangling, China

Sustainability, 2018, vol. 10, issue 8, 1-21

Abstract: To examine the effect of green roofs (GRs) and green walls (GWs) on coarse particle (PM 10 ) dispersion in urban street canyons, a computational fluid dynamics (CFD) simulation was conducted with a Reynolds-averaged Navier-Stokes (RANS) model and a revised generalized drift flux model. Simulations were performed with different aspect ratios (H/W = 0.5, 1.0, and 2.0), greenery coverage areas (S = 300, 600, and 900 m 2 ), and leaf area densities (LADs = 1.0, 3.5, 6.0 m 2 /m 3 ). Results indicate that: (1) GRs and GWs all had the reduction ability of PM 10 at the pedestrian level; (2) Averaged concentrations of PM 10 in GWs and GRs varied little as LAD changed in H/W = 0.5 and 1.0. When H/W = 2.0, the aerodynamic effects of GRs increased since airflow was enhanced within street canyons, resulting in the increasing concentrations in GRs compared with non-greening scenarios; (3) Given equal greenery coverage area and aspect ratio, GWs are more effective in reducing street-canyon PM 10 , and the averaged concentrations declined with increasing LADs and greenery coverage areas, especially the H/W; (4) At the pedestrian level, the reduction ratio of GRs is greater than that of GWs with the maximum value of 17.1% for H/W = 0.5. However, where H/W = 1.0 and 2.0, the concentrations within GWs are lower than GRs, with maximum reduction ratios of 29.3% and 43.8%, respectively.

Keywords: green roofs; green walls; computational fluid dynamics; PM 10; greenery coverage; street canyon (search for similar items in EconPapers)
JEL-codes: O13 Q Q0 Q2 Q3 Q5 Q56 (search for similar items in EconPapers)
Date: 2018
References: View references in EconPapers View complete reference list from CitEc
Citations: View citations in EconPapers (4)

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